HOA single unit activation

Sorry you're getting the runaround. For Satellite, DIRECTV recommends obtaining written or verbal approval from your landlord or homeowners' association first, before placing an order to ensure we have permission to install the service. Grab the written permission form here: DIRECTV Landlord Approval Form - Legal Policy Center

For Streaming (no dish required), installation is simpler and may not require HOA approval, but you must ensure your internet meets the minimum speed requirement (25 Mbps). More info here: Sign up for DIRECTV Streaming | DIRECTV Support Rhyan, DIRECTV Community Team

To clarify, the HOA cannot deny you having DirecTV service. You can install the receiving dish in an area under your direct control, within reason per Federal Regulation. See OTARD.

https://www.fcc.gov/media/over-air-reception-devices-rule 

The permission letter is more of a protection (for both you and them) confirming all are on the same page.

However, you say your "unit". If this is not a house, but something like an apartment building, condo, etc. then this may be a Multi Dwelling Unit (MDU) account type. With an MDU, you cannot order service directly through DirecTV. Instead you have to go through your facility's System Operator, essentially a 3rd party contracted to sell and maintain service for where you live. These often have a single dish that all residents are networked into. If this is your situation, then you need to contact your apartment manager (or equivalent authority) to find out who your System Operator is.